An attempt at improving cross-distribution software deployment: The Psys Library

[Denis Washington]

Hi,

Cross-distribution software deployment on Linux remains to be a big 
problem. Basically, an independent software provider (ISV) has two choices:

- Creating separate packages for every distribution (or, at least, every 
package format). This provides a high level of integration with the 
distribution, but is a relatively high investment for an ISV, which must 
not understand only one, but multiple packaging systems. Also, this 
approach doesn't help users of smaller distributions with 
less-mainstream packaging systems, for which most probably no packages 
will be built.

- Bypassing the package manager completely by deploying an executable 
installer which essentially just copies files. This has the obvious 
advantage of really working on any distribution, and also lowers the 
level of investment required by the ISV remarkably (especially if the 
software is deployed with a cross-platform installer framework, which 
requires the ISV to develop only one solution for all supported 
operating systems). But the equally obvious disadvantage is the complete 
lack of integration; the package manager has no control over the 
installation and cannot avoid conflicts with other packages, and users 
cannot manage (e.g. uninstall) the software with their distribution's 
software management tools.

As can be seen quickly, both solutions are far from optimal.

In 2006, the Free Standards Group (the organisation behind the LSB, 
whose CTO was Debian founder Ian Murdock at that time) attempted to do 
better. In an LSB face-to-face meeting in Berlin, attended by several 
representatives of major distributions (including Red Hat, Novell, 
Mandriva and Ubuntu) and ISVs, the topic was discussed. The approach 
promoted by Murdock, and generally agreed upon by the attendants, was to 
bridge the gap between executable installers and package managers with a 
simple LSB-standardized programming interface - later codenamed the 
"Berlin Packaging API". The idea was to enable installer programs to 
tell the package manager when they install or uninstall software, giving 
the package manager the opportunity to update its package database 
accordingly [1]. Unfortunately, this idea didn't seem to be followed by 
any kind of standards process or implementation effort, and so the 
project eventually died.

Today, I am pleased to announce a project to you which tries to reignite 
the Berlin Packaging API effort with a concrete design and a 
proof-of-concept implementation ready for testing: the "Psys Library". 
 From the README:

"The psys library provides a simple interface to the system package 
managerof a Linux system. It allows installation programs to notify the 
packagemanager of the installation, uninstallation and update of 
third-partysoftware packages, and to request these packages to be added 
to or removed from the system package database. The psys library 
interface is generic and not tied to a specific package management 
system or Linux distribution.

Note that the psys library is only useful for adding and removing 
software which complies to the Linux Standard Base (LSB) specifications. 
Most notably, it is assumed that the data files of a software package 
are installed into /opt as demanded by the Filesystem Hierarchy Standard 
(FHS), and that a package only depends on the interfaces and behavior 
specified by the LSB; any additional dependencies must be contained 
within the package itself.

The psys library interface is strongly influenced by the Berlin 
Packaging API concept discussed at the 2006 LSB face-to-face meeting in 
Berlin. The library interface is meant as a proposal for a future 
version of the LSB standard."

More information, including the complete API documentation and a link to 
the git repository with the source code, can be found on the project 
page [2].

Now, I am asking you for support. While the psys library in its current 
form does, in fact, already offer basic integration into RPM- and 
Debian-based distributions through "fallback backends" (see the project 
wiki), the greatest level of integration can only be received if the 
implementation is provided by distributions directly. The question is: 
can you imagine adding support for a programming interface like this in 
your distribution? If not, why? And if you do, what do you think of the 
psys API in its current form? Where do you think it is lacking? Flawed? 
Complete BS?

I am thrilled to hear your replies, and hope we can all together make 
something happen to improve the state of third-party software deployment 
on Linux.

Best regards,
Denis Washington

[1] http://www.linuxfoundation.org/en/Berlin_Packaging_API
[2] http://gitorious.org/libpsys

P.S.: You might remember an earlier (2008), somewhat over-engineered 
attempt of mine to implement the Berlin Packaging API concept, the 
"Burgdorf Packaging API" 
(http://www.linuxfoundation.org/en/Burgdorf_Packaging_API), which 
spawned quite a lot of discussion at that time. Let me assure you, 
though, that the psys library is much simpler (and also already more 
advanced) in design and implementation than Burgdorf, and much lighter 
in terms of dependencies (libc, essentially).